Theorem tpid2 4734

Description: One of the three elements of an unordered triple. (Contributed by NM, 7-Apr-1994.) (Proof shortened by Andrew Salmon, 29-Jun-2011.)

Hypothesis

Ref	Expression
tpid2.1	⊢ 𝐵 ∈ V

Assertion

Ref	Expression
tpid2	⊢ 𝐵 ∈ {𝐴, 𝐵, 𝐶}

Proof of Theorem tpid2

Step	Hyp	Ref	Expression
1		eqid 2762	. . 3 ⊢ 𝐵 = 𝐵
2	1	3mix2i 1353	. 2 ⊢ (𝐵 = 𝐴 ∨ 𝐵 = 𝐵 ∨ 𝐵 = 𝐶)
3		tpid2.1	. . 3 ⊢ 𝐵 ∈ V
4	3	eltp 4653	. 2 ⊢ (𝐵 ∈ {𝐴, 𝐵, 𝐶} ↔ (𝐵 = 𝐴 ∨ 𝐵 = 𝐵 ∨ 𝐵 = 𝐶))
5	2, 4	mpbir 234	1 ⊢ 𝐵 ∈ {𝐴, 𝐵, 𝐶}

This proof depends on syntax axioms:   ∨ w3o 1102   = wceq 1570   ∈ wcel 2145  Vcvv 3453  {ctp 4591

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1828  ax-4 1842  ax-5 1943  ax-6 2000  ax-7 2041  ax-8 2147  ax-9 2155  ax-ext 2734

This proof depends on definitions:  df-bi 210  df-an 402  df-or 862  df-3or 1104  df-tru 1573  df-ex 1813  df-sb 2100  df-clab 2741  df-cleq 2754  df-clel 2837  df-v 3455  df-un 3907  df-sn 4588  df-pr 4590  df-tp 4592

This theorem is used by:  1eltp012  12338  hash3tpb  14562  sgncl  15172  degenmgm2nfun  19053  sgnsf  33589  signsw0glem  35048  signsw0g  35051  signswmnd  35052  signswrid  35053  kur14lem7  35778  brtpid2  36288  rabren3dioph  43643  oenord1ex  44143  oenord1  44144  fourierdlem102  47023  fourierdlem114  47035  etransclem48  47097  usgrexmpl1tri  48928  usgrexmpl2nb3  48937  usgrexmpl2nb4  48938  usgrexmpl2nb5  48939